PURPOSE: The primary objectives of this phase I study are to compare the safety, dose response, pharmacodynamic and pharmcokinetic properties of filgrastim-SD/01 to filgrastim. Filgrastim-SD/01 has not yet been tested in humans. Filgrastim-SD/01 is filgrastim (G-CSF, Neupogen) covalently bound at the N-terminus with a polyethylene glycol (PEG) molecule. Pegylation of a protein decreases the clearance and increases the half-life of compounds, resulting in a sustained duration effect. Filgrastim is a lineage-specific hematopoietic growth factor that preferentially stimulates the growth, differentiation and function of neutrophils. It has been approved by the FDA for chemotherapy-induced neutropenia, bone marrow transplantation, severe chronic neutropenic and stem cell mobilization. Filgrastim-SD/01 offers the advantage that similar pharmacologic effects identical to repeat injections of filgrastim can be obtained from a single injection. Potential benefits would include fewer injections, increased patient compliance, uninterrupted therapy over periods of time when the patient cannot visit clinics, and reduced burden on medical support staff. METHODS: This study is directed at patients with non-small cell lung cancer requiring chemotherapy. The study will be done in two parts, dosing with study drug pre and post one cycle of carboplatin/paclitaxel chemotherapy. The total duration of the study is five weeks. Patients will be randomized (3:1) to receive either filgrastim-SD/01 or Neupogen throughout the study. During part A, pre-chemotherapy, patients randomized to receive study drug will receive one injection according to dose assignment on day 1. Patients randomized to G-CSF will receive subcutaneous injections at 5 ug/kg/day for five days or until the ANC reaches 75,000. Patients will have daily blood draws for 12 days in a row for routine blood counts and chemistries, pharmacokinetics, and CD34 analysis. The chemotherapy will consist of carboplatin (AUC of 6, 30 min infusion) plus paclitaxel (24 hour infusion, 225 mg/M2). Twenty-four hours after completion of chemotherapy, patients will receive study drug or G-CSF at the dose given in part A. Patients on G-CSF will be dosed at 5 ug/kg/day until ANC > l0,000. There will be daily blood draws for 15 days in a row during part B for analyses similar to part A. Pharmacokinetic and pharmacodynamic methods will be used to compare G-CSF and filgrastim-SD/01 in parts A and B. Descriptive statistics will be used to characterize the neutrophil and CD34 counts during part A. Generalized linear models will be used to estimate the association of filgrastim-SD/01 dose on neutrophil responses in part B. This neutrophil response will be measured by the need for G-CSF rescue as well as duration of severe neutropenia. The proportion of patients in each dosing group who require G-CSF rescue will be descriptively compared to the proportion of patients in the G-CSF group who met the criteria for rescue. It is expected that the side effect profile of this drug will mimic that of G-CSF, with the most common adverse reaction being bone pain. It is possible, because of the sustained action of the study drug, that bone pain may be more severe and/or of longer duration than that associated with G-CSF. RESULTS: Twelve of thirteen enrolled patients completed the study. Side effects were limited to bone pain which was mild to moderate in intensity, similar to standard filgrastim at all dose levels. There was a dose response effect with respect to the degree of neutrophil elevation and its duration and in terms of the number of progenitor cells mobilized. The study was presented as an abstract at the American Society of Clinical Oncology in May, 1998. A manuscript is in progress. SIGNIFICANCE: This study may contribute to an improved form of therapy for chemotherapy induced neutropenia. The future plans will depend on the results of this trial.